Does range have to calculate all previous values when using a index

Question

In python 3, range supports indexing but I am wondering exactly how that works.

For example: range(100000000000000000000000000)[-1]

I have a basic understanding that the range function actually returns a range object that takes up a limited amount of memory. Does that mean that to get to the last value, it has to calculate all the previous values?

Answer 1

It is not required to get previous value to get the last value.

It is computed by compute_item function (which is called by compute_range_item <- range_item ...).

From Python 3.3 source code (Objects/rangeobjects.c)

static PyObject *
compute_item(rangeobject *r, PyObject *i)
{
    PyObject *incr, *result;
    /* PyLong equivalent to:
     *    return r->start + (i * r->step)
     */
    incr = PyNumber_Multiply(i, r->step);
    if (!incr)
        return NULL;
    result = PyNumber_Add(r->start, incr);
    Py_DECREF(incr);
    return result;
}